The hot-dip galvanization has been used widely as a technique for improving the corrosion resistance of a steel material.
JP2009-221601A, JP2009-221604A, JP2009-197328A, JP2011-26630A, and JP2009-221605A describe methods of manufacturing a hot-dip galvanized material in which, even if a molten zinc bath in which the content of Pb is restrained to at most 0.1 mass % and the content of Cd is restrained to at most 0.01 mass % is used in conformity to the RoHS instructions, poor plating occurs infrequently. In the methods of manufacturing a hot-dip galvanized material described in these Patent Documents, a metal such as Sn, Sb, Bi, or In is added to the molten zinc bath in minute amounts.
JP2006-307316A describes a hot-dip galvanizing bath composition for forming a galvanizing film on the surface of a steel material by means of a dipping process. The hot-dip galvanizing bath composition consists of 0.01 to 0.05 wt % of Ni, 0.001 to 0.01 wt % of Al, and 0.01 to 0.08 wt % of Bi, the balance being Zn and unavoidable impurities, and not containing Pb.
JP2011-26632A describes a hot-dip galvanized steel material in which the composition of the plating layer contains at most 0.010 mass % of Pb and 0.04 to 0.50 mass % of Sb.
JP10-140316A describes a method of manufacturing a hot-dip galvanized steel material in which a steel plate, which is plated by using a hot-dip galvanizing bath containing 0.1 to 0.3 wt % of Al and at most 0.01 wt % in total of Pb, Sn, Cd and Sb as impurities, is subjected to rolling with a rolling weight of 50 to 500 tons per 1 m width of steel plate that is in contact with a roll.
JP2011-89175A describes a hot-dip galvanized steel pipe in which the lead concentration in a hot-dip galvanizing film is at most 0.1 mass %, the cadmium concentration therein is at most 0.01 mass %, and the Vickers hardness of an alloy layer part of the hot-dip galvanizing film is at most 110 Hv.